Mecanum Wheel

A from-scratch design of a mecanum wheel (https://en.wikipedia.org/wiki/Mecanum_wheel), intentionally scaled and designed to mimic the size and shape of a typical filament spool.

Printed parts:

All parts: 0.2mm layer height, 8 top layers, 8 bottom layers, 3 walls w/ 0.4mm nozzle.

The Main Body (print 2) and Roller Shafts (print 12) should be printed in PLA or PETG (or other rigid material). Overhung holes and and small flat surfaces are specially designed to print without supports using the above parameters. The Roller Shaft on has this no-supports-needed design on one end, so be sure that end is face-down on the print bed.

The Roller Sleeves (print 12) should be printed in TPU (or other grippy material) to provide traction. Layer height probably doesn't matter too much, but I applied manual seam control to ensure that outer surface and inner surface seams were on a diagonal around the sleeve and staggered (outer and inner seams set 180° apart) to ensure the thin-walled TPU parts wouldn't be prone to splitting apart at the seams (literally) when stretched over the shafts. I applied a very small degree of Fuzzy Skin (0.1mm thickness, 0.5mm distance) to the outside walls only to increase the texture and grippiness (and maybe help to camouflage the seams a bit).

Additional Hardware Required:

• 12x M6x10mm hex socket cap bolts
• 24x skateboard bearings (22mm OD, 8mm ID, 7mm width/thickness)

Assembly:

1. Slide a Roller Sleeve onto each Roller Shaft (x12). This will require some force as the TPU sleeve has to stretch to fit over the end of the shaft.
2. Insert a bearing into each end of each shaft (x24). The model is designed to be slightly oversized, but with small well-fitted ridges to hold the bearing snugly. It shouldn't require too much force to insert them, and they could be removed again if necessary without destroying the shaft.
3. Place one Main Body part face-down and fit the end of one Roller onto each of the 12 mounting points. The bearings should fit snugly on the posts but not require much force to fit.
4. Apply the 2nd Main Body part on top of the assembly. Verify that the bolt holes (the non-threaded through-holes with wide chamfers) are aligned with the threaded holes of the other Main Body part. [Note, the model file is correct, w/ 6 recessed and chamfered holes. The photo is of an earlier version where all 12 holes were inadvertently recessed and chamfered making it hard to tell which ones to put the bolts in.] The holes won't line up perfectly until the assembly of this stage is complete, but if you wind up with the bolt holes and threaded holes incorrectly staggered, rotate the upper Main Body part by 1/12th of a rotation (30°) and try again. Start by aligning one mounting post with the bearing of one Roller Shaft, then working your way around the remaining mounting points until all twelve bearings are fitted into place.
5. With all 12 rollers fitted to the mounting points of both Main Body parts, ensure the bolt holes are aligned and place 6x M6-10mm hex socket cap bolts into the chamfered bolt holes and finger-tighten each bolt on opposing sides of the wheel axis.
6. Flip the wheel over and apply 6 more bolts same as above.
7. Go back to the first side, and finish tightening those 6 bolts, then finish with tightening the 6 bolts on the second side.

Mounting the wheel:

The threaded holes in the Main Body for bolting the two halves together also extend all the way through the body, so are accessible from the outside for attaching any kind of shaft or pulley-based drive system applicable for your application.

Styling:

Since I don't built robots or vehicles that would benefit from mecanum wheels, I designed this project as a CAD skills exercise. Since my finished wheel will only be a showpiece, and to further increase the appeal of the finished product, I printed two of each Roller Shaft in Pride rainbow colours, and placed same-colour rollers 180° apart on the wheel. I then used transparent TPU for the Roller Sleeves to allow more of the shafts' colours to be visible. Alternatively, if you have a wide variety of colours of TPU available, you could print them in colours that match their respective rollers. Be creative! Or be boring and print it all monotone. It's your wheel.